Spectrotemporal analysis of evoked and induced electroencephalographic responses in primary auditory cortex (A1) of the awake monkey

Cereb Cortex. 2008 Mar;18(3):610-25. doi: 10.1093/cercor/bhm094. Epub 2007 Jun 22.


Electroencephalography is increasingly being used to probe the functional organization of auditory cortex. Modulation of the electroencephalographic (EEG) signal by tones was examined in primary auditory cortex (A1) of awake monkeys. EEG data were measured at 4 laminar depths defined by current source density profiles evoked by best frequency (BF) tones. Midlaminar multiunit activity was used to define the tuning characteristics of A1 sites. Presentation of BF tones increased EEG power across the range of frequencies examined (4-290 Hz), with maximal effects evident within the first 100 ms after stimulus onset. The largest relative increases in EEG power generally occurred at very high gamma frequency bands (130-210 Hz). Increases in EEG power for frequencies less than 70 Hz primarily represented changes in phase-locked activity, whereas increases at higher frequencies primarily represented changes in non-phase-locked activity. Power increases in higher gamma bands were better correlated with the A1 tonotopic organization than power increases in lower frequency bands. Results were similar across the 4 laminar depths examined. These findings highlight the value of examining high-frequency EEG components in exploring the functional organization of auditory cortex and may enhance interpretation of related studies in humans.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Acoustic Stimulation / methods*
  • Animals
  • Auditory Cortex / physiology*
  • Electroencephalography / methods*
  • Evoked Potentials, Auditory / physiology*
  • Haplorhini
  • Macaca fascicularis
  • Male
  • Time Factors
  • Wakefulness / physiology*